Straumsvola complex, Queen Maud Land, East Antarctica, Antarcticai

Regional Level Types
Straumsvola complex	Complex
Queen Maud Land	Region
East Antarctica	Region
Antarctica	Continent

Straumsvola Mountain (72°7′S 0°20′W) is a prominent mountain 6 nautical miles (11 km) north of Jutulrora Mountain in the northwest part of the Sverdrup Mountains, overlooking the east side of Jutulstraumen Glacier in Queen Maud Land. Plotted from air photos by the German Antarctic Expedition (1938–39). Remapped by Norwegian cartographers from surveys and air photos by Norwegian-British-Swedish Antarctic Expedition (NBSAE) (1949–52) and air photos by the Norwegian expedition (1958–59) and named Straumsvola (the stream mountain). [Wikipedia]

Straumsvola is a nepheline syenite intrusive complex about 7 km in diameter, which intrudes gneisses of the Jutulrøra Formation (Svedrupfjella Group), located on the eastern edge of the Jutulstraumen Glacier (Ravich & Solov'yev, 1966 and 1969; Hjelle, 1972; Allen et al., 1986; Harris & Grantham, 1993). The Straumsvola nepheline syenite complex consists of a massive outer zone and a layered inner zone, whereas the adjacent nunatak 5 km to the southeast, Tvora, consists of quartz syenite (see http://www.mindat.org/loc-266652.html). The Straumsvola complex is exposed mostly on the nunatak Straumsvola itself, but it can be observed also at the easternmost Storjoen and Joungane nunataks.

The outer zone contains numerous pegmatite dykes (southeast ridge of Straumsvola and summit ridge of Storjoen) consisting of alkali feldspar, biotite, sodium-rich pyroxene, and amphibole. Such pegmatite dykes can contain cavities up to several metres in diametre, in which large, well-formed crystals of feldspar, amphibole, aegirine, zircon (up to 2 cm across), analcime, and natrolite are present. Natrolite prismatic crystals are partially enclosed by icositetrahedra of analcime.
The layered rocks are exclusively exposed on Straumsvola. Near the summit of Straumsvola, a more mafic facies unconformably overlies the layered zone.

A large number of Jurassic dykes cut the two plutons and the surrounding country-rocks. These dykes are extremely varied in composition and include nephelinites, pyroxenites, lamprophyres, dolerites, phonolites, and peralkaline microgranites. Jurassic dykes of western Dronning Maud Land dyke swarms are probably related to magmatism associated with the Karoo large igneous province in Africa.

In one unusual dyke of peralkaline granite, which crops out on the north ridge of Straumsvola at about 200 m from the summit and cuts both the nepheline syenite country-rock and several dolerite dykes, REE-rich eudialyte occurs together with the rare mineral dalyite (Harris & Rickard, 1987). In other dykes of peralkaline granite narsarsukite and vlasovite have been found (Harris & Grantham, 1993).

Eudialyte is found in fissures and vugs throughout the upper layered zone syenites and in one case as a major phase (up to 20 modal %) in a pegmatite dyke located 100 m south of Straumsvola summit (Harris & Grantham, 1993).

Geochronology

Mineralization age: Mesozoic : 206.07 ± 2.63 Ma to 170.93 ± 1.67 Ma

Important note: This table is based only on rock and mineral ages recorded on mindat.org for this locality and is not necessarily a complete representation of the geochronology, but does give an indication of possible mineralization events relevant to this locality. As more age information is added this table may expand in the future. A break in the table simply indicates a lack of data entered here, not necessarily a break in the geologic sequence. Grey background entries are from different, related, localities.

Geologic Time				Rocks, Minerals and Events
Phanerozoic
	Mesozoic
		Jurassic
			Middle Jurassic	ⓘ Nepheline-syenite (youngest age) 170.93 ± 1.67 Ma
			Early Jurassic	ⓘ Alkali Feldspar (youngest age) 178 Ma ⓘ Alkali Feldspar (oldest age) 180 Ma
		Triassic
			Late/Upper Triassic	ⓘ Nepheline-syenite (oldest age) 206.07 ± 2.63 Ma

Other Databases

Wikipedia:	https://en.wikipedia.org/wiki/Straumsvola_Mountain
Wikidata ID:	Q7622316

Other Regions, Features and Areas containing this locality

References